Automatic sheet material dispensers, such as paper towel dispensers and the like, are widely used to supply paper towel and other types of sheet material to persons in public restrooms, kitchens, food-preparation facilities and other settings in which hygiene and cleanliness are desired or in which sheet material is desired for some other purpose. The sheet material dispensed by these dispensers is typically in the form of a web wound into a roll on a core. The sheet material is unwound from the roll by the dispenser and is dispensed to the user.
A typical automatic paper towel dispenser is a battery-operated device with a direct current (DC) motor that is activated by a proximity sensor or contact switch. A controller controls the DC motor to dispense a predetermined amount of sheet material (e.g., 12 inches) for each activation of the proximity sensor or contact switch.
A problem with automatic sheet material dispensers, such as paper towel dispensers and the like, is that it can be difficult for the attendant to determine the amount of sheet material remaining on the roll and to determine whether a replacement roll should be loaded in the dispenser. It can be difficult to determine the amount of material remaining in the dispenser because the roll typically cannot be seen within the opaque dispenser housing. Therefore, the attendant must manually unlock and open the dispenser to view the roll and to determine whether a replacement roll should be loaded into the dispenser. This is time consuming and inconvenient for the attendant, particularly in facilities such as public restrooms which may include many dispensers. Obviously, it is important that the automatic sheet material dispenser have a supply of material because the dispenser cannot be used if there is no material available to be dispensed.
A paper towel dispenser with a low-paper indicator has been proposed as described in International Publication No. WO 2007/068270A1. The paper towel dispenser described in this document uses an angular displacement measurement system which may lack accuracy and requires parts which may increase the dispenser cost.
Automatic paper towel dispensers which detect loading of a proper roll of paper towel are known as described in U.S. Pat. No. 7,040,566 (Rodrian et al.). Also known are motor pulse counting techniques used to turn a paper towel dispenser motor “on” and “off” to dispense a length of paper as described in U.S. Pat. No. 7,084,592 (Rodrian). These technologies have not been utilized to control dispenser operation to indicate a low-material state.
Accordingly, what is needed are techniques to control automatic sheet material dispenser apparatus to indicate a low-material state which are efficient, cost effective, and which generally provide an improved dispenser.